Explain the role of racial prejudice in the novel To Kill a Mockingbird.

On one level, To Kill a Mockingbird
is a commentary on race relations in the South during the Great Depression. 
As Scout and Jem get older, they begin to perceive explicit differences in the attitudes
of people in the community towards blacks.  Atticus, for example, believes in the
dignity and worth of all people, regardless of race, and this shows in his words and
actions, not the least of which is his decision to represent Tom Robinson to the best of
ability, even though he knows from the beginning that he will lose.  The Ewells,
residing at the very bottom of the social structure, rely on blacks to provide them
something to feel superior to; therefore, their prejudice toward blacks is absolutely
necessary.  Many, if not most residents of Maycomb County share the belief that as
disgusting as the Ewells are, they are still white, and therefore inherently better than
blacks.